For example, a liquid crystal panel for use in a liquid crystal display device such as a liquid crystal television set, does not emit light and thus needs a backlight unit as a separate lighting device. The backlight unit is mounted on the back side of the liquid crystal panel (opposite to a display surface), and includes a chassis with an open surface on the liquid crystal panel side; a light source (cold cathode tube or the like) housed in the chassis; an optical member (diffuser sheet or the like) disposed at the opening of the chassis and efficiently discharging light from the light source toward the liquid crystal panel; and a reflection sheet laid in the chassis and reflecting light from the light source toward the optical member and the liquid crystal panel. In addition, as an example of this kind of a backlight unit, there is a well-known backlight unit disclosed in Patent Document 1 shown below.    Patent Document 1: Japanese Unexamined Patent Publication No. 2006-146126